Arc Flash Calculator

What Is an Arc Flash?

An arc flash is a sudden release of electrical energy through the air. It occurs when insulation or isolation between electrical conductors breaks down.

This event can produce:

• Extreme heat (over 19,000°C)
• Intense light
• Pressure waves
• Flying molten metal

Even a short arc flash can cause severe burns, blindness, hearing damage, or death.

That is why arc flash analysis is not optional—it is a safety necessity.

Why an Arc Flash Calculator Is Important

An arc flash calculator helps you:

• Estimate incident energy at a working distance
• Identify the arc flash boundary
• Determine the required PPE category
• Assess the overall hazard risk level

This information is essential for:

• Electrical safety planning
• Arc flash labeling
• PPE selection
• Compliance with safety standards

Without these calculations, workers may be under-protected or exposed to life-threatening risks.

Standards Behind Arc Flash Calculations

Most modern arc flash calculators are based on IEEE 1584, the globally accepted standard for arc flash hazard calculations.

IEEE 1584 considers:

• System voltage
• Fault current
• Equipment type
• Electrode configuration
• Clearing time of protective devices
• Working distance

The calculator you shared uses simplified forms of these equations to provide planning-level estimates.

Important: Calculator results are for guidance only. A full arc flash study must be performed by a qualified professional.

Key Inputs Used in the Arc Flash Calculator

Let’s break down each input field in simple terms.

1. System Voltage (kV)

This is the operating voltage of the electrical system.

Examples:

• 0.48 kV (480 V)
• 4.16 kV
• 13.8 kV

Higher voltage generally means:

• Higher arc energy
• Greater hazard potential

2. Available Fault Current (kA)

Fault current is the maximum current that can flow during a short circuit.

• Measured in kiloamperes (kA)
• Depends on transformers, generators, and system impedance

Higher fault current usually increases:

• Arc current
• Incident energy

3. Breaker Clearing Time (Seconds)

This is the time taken by protective devices (breakers or relays) to interrupt the fault.

Why it matters:

• Longer clearing time = more energy released

Even a small increase in clearing time can greatly raise incident energy.

4. Electrode Gap Configuration

This defines how conductors are arranged during an arc.

Common configurations include:

• Vertical electrodes in open air
• Vertical electrodes in an enclosure
• Horizontal electrodes

Enclosed and horizontal configurations often produce higher incident energy because heat is trapped and directed outward.

5. Working Distance (Inches)

Working distance is the distance between the worker’s face or chest and the arc source.

Typical values:

• 18 inches
• 24 inches
• 36 inches

Closer distance = higher exposure = higher incident energy.

6. Equipment Type

Different equipment behaves differently during an arc flash.

Examples:

• Low voltage panels
• Motor control centers
• Medium voltage switchgear
• Transformer secondary

The calculator applies an equipment factor to adjust energy levels based on real-world behavior.

What the Arc Flash Calculator Calculates

Once inputs are entered, the calculator provides four main results.

1. Incident Energy (cal/cm²)

Incident energy measures the thermal energy a worker receives during an arc flash.

• Measured in calories per square centimeter
• Directly linked to burn severity

General reference:

• 1.2 cal/cm² → Onset of second-degree burn
• Above 40 cal/cm² → Often considered extremely dangerous

2. Arc Flash Boundary (Inches)

The arc flash boundary is the distance at which incident energy drops to 1.2 cal/cm².

• Inside the boundary → PPE required
• Outside the boundary → Lower risk

This boundary helps define restricted work zones.

3. PPE Category

The PPE category tells you what level of protective clothing is required.

Typical categories:

• CAT 1: Light protection
• CAT 2: Moderate protection
• CAT 3: Heavy protection
• CAT 4: Maximum protection
• CAT 4+: Extreme hazard

Higher categories mean:

• Thicker arc-rated clothing
• Face shields, gloves, and hoods

4. Hazard Risk Category

This is a simplified risk label:

• Low
• Medium
• High
• Very High
• Extreme

It helps non-technical users quickly understand the danger level.

How the Calculator Works (In Simple Terms)

Internally, the calculator:

1. Converts fault current and voltage into logarithmic values
2. Estimates arc current using IEEE-based equations
3. Calculates incident energy using:
   • Arc current
   • Clearing time
   • Working distance
   • Equipment factor
4. Computes the arc flash boundary
5. Assigns PPE and risk categories based on energy levels

All calculations are automated, so users only need to input values.

Practical Example

Imagine this scenario:

• Voltage: 13.8 kV
• Fault current: 25 kA
• Clearing time: 0.083 seconds
• Working distance: 24 inches
• Equipment: Medium voltage switchgear

The calculator may show:

• Incident energy: High
• Arc flash boundary: Several feet
• PPE category: CAT 3 or CAT 4
• Risk level: Very High

This tells you:

• Heavy PPE is required
• Only trained personnel should perform work
• Faster protection settings could reduce risk

Limitations of an Online Arc Flash Calculator

While helpful, calculators have limits.

They do not:

• Replace detailed arc flash studies
• Account for all system complexities
• Include protection coordination analysis
• Replace professional engineering judgment

Always treat results as estimates, not final safety approval.

Best Practices for Using an Arc Flash Calculator

• Use accurate fault current data
• Verify breaker clearing times
• Choose correct equipment type
• Recalculate after system changes
• Combine calculator results with site safety rules